Process for electrodepositing lead upon iron



Patented Aug, 19, 1924.

BERTBAND S. SUMMERS, F PORT HURON, MICHIGAN.

PROCESS FOR ELECTRODEPOSITING LEAD UPON IRON. A

Io Drawing.

1 '0 all whom it may concern:

Be it known that I, BERTRAND S. SUM- MEns,-a citizen of the United States, residing. at Port Huron, inthe county of St.

5 Clair and State of Michigan, have invented certain new and useful Improvements in Processes for Electrodepositing Lead U on Iron, of which the following is a speci oation.

It has long been a matter of common practice to line iron pipes and to cover other articles of iron with a thin lead coatin order to protect them from rust, particu arly where they are exposed to moisture. This coating is ordinarily applied by electro deosition from an aqueous bath or solution.

t has been found difiicult or impossible heretofore to produce in this manner .a dense homogeneous coating of the metal which is uniformly adherent and of good appearance,

particularly where a suflicient current density is employed to meet the demand of rapid operation. While my invention is primarily designed for plating iron, it is obvious that other metals may be used where a suitable protective coating is desired.

By the invention which forms the subject matter of this application I have been able to rapidly form a dense coating of -the required thickness which is tenaciously adherent throughout and substantially free from discoloration; In my improved rocess for deposit-inglead on iron I emp oy a solution of lead acetate and anodes of aluminum. Preferably and in the specific example of the invention herein given, the-acetate of lead-is dissolved-in a bath of acetate of aluminum containing also acetate of. lime formed by dissolving alum in acetate of lime. I prefer to use the crude form of the acetate of lime on account of the impurities found therein which are of organic nature due to the source of the acetate of lime andform a suitable colloid which tends to prevent the formation of sponge during the plating. The acetate of lime is pr erably used in excess for this reason. the electrolytic bath formed in this way the metal forming the cathode receives a much more uniform, denser coat free from stain and'amuch higher current density can be used in the operation which naturally cuts down the required time. The explanation of the su erior results is not definitely known but the ions of aluminum undoubtedly have some efl'ect in aiding"-the-deposi- Application filed February 23, 1923. Serial 1T0. 620,825.

tion of the lead upon the cathode and alloy-i ing with the same and the electro-chemical equivalent of aluminum is very much smaller than lead, the deposition naturally consists chiefly of lead. The deposition formed is very resistant to acids and forms an ad- .mirable protective coating.

It has been found diflicult to plate lead from its salts and in the. cases where this has been done, it is usually necessary to keep the current density rather low to avoid forming trees or sponges. I have discovered that if a compound anode is used, that is, lead and aluminum, a coating is plated on the cathode which is very dense, resistant to acids, and which may be plated with a high current density.

As a specific illustration ,of the practice of my improved process I give the following: 500 pounds of alum and 1000 poundsof acetate of lime were dissolved in about ticle to be coated, after being pickled and cleaned in the usual manner, was connected as the cathode and aluminum anodes were employed, the anodes and cathodes being connected up to a suitable source of direct current. At the outset the current employed was small, about two amperes or less per square foot of the cathode surface being employed, and as the initial film formed the current density was gradually increased until it amounted to ten amperes per square foot. The plating operation was continued with the ter current density until a plating of the desired thickness had been deposited. The temperature employed was very slightly above the atmospheric temperature at the time, though it might have been slightly greater or less without materially affecting the result. After the desired thickness had been deposited, the pipe was removed from the bath and thoroughly washed to cleanse it of the electrolyte- The resultant coating was an allo of lead containin a small ercentage of a uminum and was ense, uni orm in color and thick- I claim:

1. A process of electro-plating lead on iron which consists in forming a solution of lead, immersing the iron to be treated therein, immersing aluminumanodes therein and connecting the anodes and the iron,

cathodes with a suitable source of direct current.

A process of plating lead on iron which' 1 from the anodes through the electrolyte to the cathodes and gradually increasing the current density.

3. A process of electro-plating iron with lead which consists in forming an electrolyte containing acetate of lead, aluminum acetate and calcium acetate, immersing the iron articles to be treated as a cathode in the electrolyte, immersing an aluminum anode in the electrolyte and passing a plating current from said anode to the cathode.

4. A process of electro-plating lead on iron which consists in dissolving an aluminum salt in a solution of acetate of lime, dissolving lead acetate in the solution so formed, immersing the iron articles to be coated and aluminum anodes in the electrolyte and passing a lating current from the anodes to the cath es.

5. A process of electrolating lead on iron which consists in disso ving alum in a solution containing an excess of acetate of lime thereby forming a solution of acetate of aluminum containing acetate of lime, dissolving lead acetate in said solution to form an electrolyte, immersing aluminum anodes and the iron to be plated in the electrolyte so formed, and passing a plating current from the anode to the cathode.

6. A process of electro-plating lead on a metal base which consists in forming a solution of lead, immersing the metal, to be plated therein, and immersing in the plating bath aluminum and lead anodes and connect- .ing the anodes and the cathode formed by the metal to be plated with a substantial source of a direct current.

7 .i A process of electro-plating lead on iron which consists in eIectro-depositing lead on iron in a bath containing a soluble salt of lead and a third metal in a form in which it will not react with the lead salt.

8. A process of electro-plating lead on iron which consists in electro-depositing the lead'from a bath containing a soluble salt of lead and aluminum in a form in which it will not react with the lead salt.

BERTRAND s. SUMMERS. 

